Machado-Joseph Disease (MJD) is a dominantly inherited neurodegenerative disease. It is caused by an expansion of a normally occurring polyglutamine repeat. Proteins with expanded glutamine repeats form aggregates which are toxic to certain neurons in the brain, eventually killing them. The mechanism by which these expanded polyglutamine proteins kill specific brain cells is not well understood. To develop new drugs and therapies to stop the disease, we need to find targets for research. We have a Drosophila model of MJD which closely recapitulates the human disease. We propose to use our model to find targets for future therapies. It is our hypothesis that the proteins expressed in fly brains expressing the mutant protein will be different from fly brains expressing the normal form of the protein. Our hypothesis is based on three observations. First, genomic studies show there are differences in gene expression between model organisms expressing mutant and normal forms of polyglutamine disease genes. Second, protein aggregates formed by mutant proteins co-localize with regulators of gene activity. This may alter the numbers and levels of proteins that are eventually produced. Third, Ataxin-3, the protein coded by the MJD1 gene, has been shown to be involved directly and indirectly in gene regulation. Mutation and co-aggregation of Ataxin-3 may change its regulatory activity. However post-transcriptional, translational, and post-translational controls ultimately determine what proteins will be found in the cellular environment and in what concentration. The differently expressed proteins represent potential targets for new therapies. We also suggest that modifiers of disease progression will also change the protein environment found in cells. Based on these observations, we propose three specific aims. 1) We will compare what proteins are expressed in the diseased state and non-diseased state of Drosophila brains expressing mutant and normal forms of the Ataxin3 (MJD1) gene. 2) We will compare the protein expression profiles of flies that express mutant Ataxin3 protein alone to those that have been rescued by modifiers of degeneration. 3) We will use the power of Drosophila genetics to observe how increasing and decreasing expression of the proteins we find in aims 1 and 2 influence neurodegeneration. The proteins identified in aims 1 and 2 that influence neurodegeneration in aim 3, are likely involved in the disease mechanism. These identified proteins are good targets for future therapies. [To observe these proteins, we will use the ICAT (isotope-coded affinity tags) technique. ICAT combines multidimensional liquid chromatography with mass spectroscopy to identify and quantify proteins found in complex mixtures.] PUBLIC HEALTH RELEVANCE: The mechanism of brain degeneration by inherited polyglutamine diseases like Machado- Joseph Disease is unknown and there are no cures or therapies. In order to find targets for cures and therapies, we propose to find what proteins are being expressed in brain cells with the disease compared to brain cells without the disease. The differences in proteins found represent potential targets for cures and therapies. [unreadable] [unreadable]